To increase the production of hydrocarbons, an oil and gas well may be stimulated by using perforating and fracturing processes. Perforation involves forming holes in the casing or liner. In particular, when a zone of interest is identified, holes may be formed by mechanical cutters, explosive charges, or other means to allow fluid communication between the reservoir and the wellbore. After the casing or liner has been perforated, a plug (e.g., a bridge plug or frac plug) may be set in the wellbore for hydraulically isolating the perforated zone from lower zones in the wellbore. By isolating the perforated zone, fracturing fluid pumped into the well may be limited to the particular zone of interest. The fracturing fluid is pumped at a high pressure to fracture the formation at the perforations through the casing or liner. The high pressure of the fracturing fluid propagates a fracture in the formation, which may increase the production of hydrocarbons from that zone of the wellbore.
The process of perforating the casing and isolating the zone of interest may be repeated at multiple locations within a single wellbore. A bridge plug may then be set at the lower end of each zone of interest where perforation and stimulation is to occur. After perforation and fracturing is completed for a zone, the set bridge plug may be removed. Removal of the bridge plugs may occur by using a retrievable bridge plug, or by milling out the bridge plug. The bridge plug may be formed of various different materials (e.g., rubber, composite materials, and metals). Milling the bridge plug may therefore involve using a mill that cuts into different materials with different material properties.